This invention relates to an electrical control system, and more particularly to a novel Wireless electrical load control system Wherein control of the poWer supplied to a load may be varied from a remote location by using a remote control device not electrically wired to the load and from a local control deVice which is electrically wired to the load.
Although the invention is described with reference to the control of lighting level, it has application in other areas, such as the control of sound volume, tone or balance; video brightness or contrast; the tuning setting of a radio or television receiver and the position, velocity or acceleration of a moveable object.
Load control systems are known in which the power supplied to the load can be adjusted by control units mounted at one or more different locations remote from the power controller. The control units are typically connected to the controller using two or three electrical wires in the structure in which the load control system is used. In an advanced version of such systems, control is transferred between different locations immediately upon manipulation of a control switch without the need for any additional overt act by the user. See, for instance, copending U.S. Pat. application Ser. No. 857,739, filed Apr. 29, 1986 with U.S. Pat. No. 4,689,547, issued Aug. 25, 1987, to M. J. Rowen et al.
To permit greater user flexibility and to permit installation of a load control system with no modification of the existing wiring system in the structure, load control systems have been modified to incorporate wireless remote control units. For example, a known type of light dimming system uses a power controller/receiver/local control and a remote control transmitter for transmitting a control signal by radio, infrared, or microwave to the power controller/receiver/local control. In these systems, a switch on the transmitter or local control must typically be maintained in a depressed position until the desired light level is reached. In such a system, it is only possible to cause the light level to be raised or lowered at a predetermined fixed rate and it is not possible to select a particular light level directly, nor is there any visual indication at the transmitter of the light level selected. In such a system a lag of two to ten seconds typically exists between actuation of the transmitter or local control and achievement of the desired light level. Especially at the higher end of the range, this lag tends to limit the commercial acceptability of such systems.
Alternative load control systems have been produced that incorporate wireless remote controls where the desired light level is reached instantaneously on operation of the remote control unit. Unfortunately, these systems only allow the selection of three or four light levels that have been previously programmed at the power controller/receiver; usually it is not possible to select one of an essentially continuous range of values.
In the case of the systems using radio waves for the control signal transmission medium, the transmitter is often larger than is commercially desirable so as to accomodate the radio transmitting system, and an antenna must frequently be hung from the controller/receiver.
Remote control systems are frequently incorporated in television sets. In these systems, a switch on the transmitter must typically be maintained in a depressed position until the desired load level, e.g., volume, is reached, with a time lag typically existing between the depression of the switch and achievement of the desired load level. Model airplanes are typically controlled by remote radio control where a control signal is typically continually transmitted during the operation of the airplane. It is possible, however, to select the control signal from an essentially continuous range of values.
Generally, in the known wireless remote load control systems, both the local and wireless remote controls are of the raise/lower type described above, where a switch has to be maintained in a depressed position until the desired load level is reached. In such a system, it is not necessary for the power controller receiving signals from the local and wireless remote controls to be able to choose which control signal to respond to as a raise signal has the same effect whether it comes from the local or wireless remote controls.
However, in a wireless remote load control system wherein either the wireless remote control or local control or both adjust power to the load through a continuous range of values immediately as the control actuator of the control device is manipulated, it is necessary for the power controller to be able to choose which control signal to respond to, as the instantaneous signals from the local and remote controls will necessarily be different.